1. Field of the Invention
The present invention relates to equipment for processing television (video) signals, and more particularly, to video switching and mix/effecting equipment which switches SDTV (Standard Definition Television) signals and HDTV (High Definition Television) signals and processes the signals to produce TV signals for broadcast.
2. Description of Related Art
The SDTV broadcast such as the NTSC (National Television System Committee) standard and the like had been conventionally used. On the other hand, the HDTV broadcast, with the purpose of broadcasting a high definition video signal, has been expected and already been conducted in part by a MUSE (Multiple Sub-Nyquist Sampling Encoding) system of an analog type in Japan, for example. On the other hand, as HDTV standards applied in a broadcast station, the SMPTE standard 292M and the SMPTE standard 296M are determined to transmit and process a HDTV signal in digital form. Since the HDTV broadcast handles a large amount of information corresponding to the high definition video signal, it requires a transmission band wider than that for the SDTV broadcast.
Now preparation for digital television broadcast utilizing, e.g., a broadcast satellite or ground wave, is made. In a digital television broadcast system, MPEG coded television signals are used for increasing transmitting capacity and capability of transmitting a HDTV signal. Further, in the digital television broadcast system, plural SDTV signals can be broadcasted in multiple channels at same time due to such capability. Accordingly, it is possible to realize a broadcast system which selectively broadcasts multiple-channel SDTV-signals or a single channel HDTV-signal.
To realize the above broadcast system, a broadcast station switches the multiple-channel SDTV signals or the single channel HDTV signal for broadcasting, and also has functions to receive a plurality of source television (video) signals and to produce the video signal(s) to be broadcasted. For example, to produce a superimposed image and a split composite image, video composition processing, i.e., mix/effecting is performed in accordance with effect requirement.
Since video signals of the SDTV signal and the HDTV signal have different bands (frequencies) and formats, to perform video switching and mix/effecting, it has been conventionally necessary to provide SDTV video switching and mix/effecting equipment and HDTV video switching and mix/effecting equipment for the respective video signals. More specifically, if the SDTV signal is a serial digital component signal of the SMPTE standard 259M, its transmission speed (band) is 270 Mbps, and if the HDTV signal is a serial digital component signal of the SMPTE standard 292M, its transmission speed is 1.5 Gbps.
FIG. 8 shows a block diagram of the conventional digital broadcast system having an SDTV video switching and mix/effecting device 1 and an HDTV video switching and mix/effecting device 8. In the conventional broadcast system in FIG. 8, SDTV video signals are inputted from input terminals Is1 to Ism. Then an SDTV switcher 2 performs switching so as to select three sets of two video signals, and supplies them to video mix/effect circuits 3 to 5. The video mix/effect circuits 3 to 5 respectively combine the input two SDTV signals in correspondence with an effect image requirement, and output the combined SDTV signals, as outputs Os1 to Os3, to SDTV encoders 6e1 to 6e3. The respective encoders compression-encode the SDTV video signals of 270 Mbps into encoded signals of 6 Mbps, and supply the encoded signals to a multiplexer/selector 7.
On the other hand, HDTV video signals are inputted from input terminals Ih1 to Ihn. Then an HDTV switcher 9 performs switching so as to select two video signals, and supplies the selected signals to a video mix/effect circuit 10. The video mix/effect circuit 10 combines the input two HDTV video signals in correspondence with an effect image requirement, and outputs the combined HDTV signal, as an output Oh, to an SDTV encoder 11. The encoder 11 compression-encodes the combined HDTV signal of 1.5 Gbps into an encoded signal of 20 Mbps, and supplies the encoded signal to the multiplexer/selector 7.
The multiplexer/selector 7 multiplexes the compressed SDTV signals of the three channels, and selectively outputs the multiplexed three-channel SDTV signals or the single-channel HDTV signal.
However, in the configuration of the conventional digital broadcast system shown in FIG. 8, the video switcher and video mix/effect circuit for the SDTV video signals, and the video switcher and video mix/effect circuit for the HDTV video signals should be individually provided. Further, since the HDTV video signal has a signal rate of 1.5 Gbps and requires high-speed signal processing in the video switcher 9 and the video mix/effect circuit 10, the specification of the video switcher 9 and the video mix/effect circuit 10 becomes higher, more complicated and costly. Therefore, as a whole, the conventional digital broadcast system is large in size and cost thereof increases.
The present invention has been made in consideration of the above situation, and has its object to provide video switching and mix/effecting equipment which can perform switching and mix/effect processing on SDTV and HDTV video signals through the same circuit (hardware).
Further, another object of the present invention is to provide video switching-and-mix/effecting equipment which can eliminate the necessity of high-speed switching and mix/effect processing on HDTV video signals.
According to the present invention, the foregoing object is attained by providing video switching and mix/effecting equipment receiving a plurality of digital high definition television (HDTV) signals and a plurality of digital standard television (SDTV) signals, comprising: input conversion circuits for converting each of said HDTV signals into each set of low speed HDTV components; switching circuit for performing switching so as to select plural sets of signals from said plurality of digital STVD signals or from a plurality of corresponding components of low speed HDTV components to deliver selected plural sets of signals, the number of the plural sets of signals corresponding to the number of the low speed HDTV components converted from one HDTV signal; a plurality of signal processing circuits provided in correspondence with the number of said low speed HDTV components, for processing said selected plural sets of signals; and output conversion circuit for converting outputs of the low speed HDTV components from said respective signal processing circuits and outputting an output HDTV signal,
wherein said plurality of signal processing circuits deliver plural sets of processed video signals of said SDTV signals or a plurality of the corresponding components of low speed HDTV components in accordance with switching operation of said switching circuit.